Range formation of beech forest understory herbs – a synthetic approach based on comparative phylogeography and distribution modelling of steppe flora and fauna in inner-Alpine dry valleys

Pleistocene refugia of deciduous trees were identified in southern, central and eastern Europe; for some species the latter played a major role in postglacial re-colonization. Although forest communities dominated large parts of Europe in the Holocene, only little is known about the phylogeography of forest-understory herbs. We will reconstruct the phylogeographies of six herbs, which are strongly associated with beech, the most abundant deciduous tree of temperate Europe. Comparisons of individual phylogeographies of beech forest understory species (BFUS) to each other and to beech and ecologically similar trees will clarify whether responses to climatic changes were independent, indicating that Pleistocene vegetation types have no present-day analogues, or whether BFUS responded in a concerted manner leading to congruence of refugia and postglacial re-colonization routes. Based on this we will evaluate the role of main factors, i.e. dispersal abilities and ecological requirements of species, explaining the current geographic distribution of BFUS. Most BFUS occur only in a fraction of the distribution range of beech, which can be explained by lower migration rates and/or narrower ecological amplitude.

Current knowledge of biogeography of temperate forest herbs and the genesis of biodiversity in forests is limited by the restricted number of available studies, the low resolution of used markers, and a focus on single species. We aim to overcome these limitations in basing our research on high-resolution Restriction associated DNA sequencing and employing explorative and hypothesis-driven phylogeographic approaches partly informed by spatially and temporally explicit demographic models. Specific models will be tested applying Approximate Bayesian Computation. Congruence among the phylogeographies of studied BFUS will be tested using a hierarchical Bayesian phylogeographic approach. We will determine the range filling of BFUS using fine-scaled species distribution models. Additionally we use a spatiotemporally explicit model simulating range dynamics of plants to unravel to which degree BFUS have realized their potential distribution range.

The project will substantially contribute towards the synthesis of the full-glacial refugia of broad-leafed forest in Europe and to understand their role as drivers of current biodiversity patterns. By aiming to determine the major factors controlling the spread of species, our approach tackles a central issue in evolution, ecology, and conservation biology. The research combines the competence of scientists from the fields of phylogeography, vegetation ecology and distribution modeling and plant sociology.